High corrosion-resistant, high-strength and non-magnetic stainless steel, high corrosion-resistant, high-strength and non-magnetic stainless steel product and method for producing the same

ABSTRACT

The present invention provides a high corrosion-resistant, high-strength and non-magnetic stainless steel containing: C: 0.01% to 0.05% by mass, Si: 0.05% to 0.50% by mass, Mn: more than 16.0% by mass but 19.0% by mass or less, P: 0.040% by mass or less, S: 0.010% by mass or less, Cu: 0.50% to 0.80% by mass, Ni: 3.5% to 5.0% by mass, Cr: 17.0% to 21.0% by mass, Mo: 1.80% to 3.50% by mass, B: 0.0010% to 0.0050% by mass, O: 0.010% by mass or less, and N: 0.45% to 0.65% by mass, with the balance substantially composed of Fe and unavoidable impurities, the steel satisfying the following equations (1) to (4): 
       [Cr]+3.3×[Mo]+16×[N]≧30   (1) 
       [Cr]/[C]≧330   (2) 
       [Cr]/[Mn]&gt;1.0   (3) 
       ([Ni]+3×[Cu])/([Cr]+[Mo])&gt;0.25   (4) 
     wherein [Cr], [Mo], [N], [C], [Mn], [Ni] and [Cu] represent the content of Cr, the content of Mo, the content of N, the content of C, the content of Mn, the content of Ni, and the content of Cu in the steel in terms of mass %, respectively.

FIELD OF THE INVENTION

The present invention relates to a high corrosion-resistant,high-strength and non-magnetic stainless steel, a high-strength, highcorrosion-resistant and non-magnetic stainless steel product and amethod for producing the same. More particularly, the invention relatesto a technique for producing a non-magnetic stainless steel which iscapable of blocking the influence of earth magnetism and is particularlysuitable for the use in oil well excavation, without impairing itscharacteristics (high corrosion resistance and high strength).

BACKGROUND OF THE INVENTION

Conventionally, when an oil well is excavated using a drill, a position(for example, direction and inclination) of a tip of the drill from theearth's surface is identified by magnetic sensing to control the drill.Accordingly, a measuring instrument is mounted in a drill collar in thevicinity of a bit. In that case, for measuring the direction andinclination, the drill collar and the like are required to be made of anon-magnetic steel, in order to block the influence of earth magnetism.Conventionally, as steels for such a use, there have been used highMn-based non-magnetic stainless steels such as 13Cr-18Mn-0.5Mo-2Ni-0.3N,13Cr-21Mn-0.3N and 16.5Cr-16Mn-1Mo-1.3Ni-0.5Cu-0.4N.

Further, as well-known improved techniques of this kind, there have beenproposed, for example, techniques described in the following patentdocuments.

Patent document 1 (JP-A-53-117618) discloses a high-strength austeniticstainless steel containing C: 0.15% or less, Si: 0.1 to 2.0%, Mn: 7.0 to18%, Ni: 0.50 to 6.0%, Cr: 15.0 to less than 21.0%, Mo: 0.5 to 4.0%, N:0.20 to 0.60% and the balance composed of Fe and impurities, which isfor the use to a body of rotation of a centrifuge or the like.

Patent document 2 (JP-A-59-104455) discloses a ultra-low temperaturehigh-strength steel excellent in rust resistance, which contains C: 0.01to 0.20 wt %, Si: 0.05 to 1.5 wt %, Mn: 16 to 27 wt %, Cr: 10 to 20 wt%, Cu: 0.1 to 4 wt %, N: 0.10 to 0.50 wt %, Al: 0.003 to 0.20 wt % andthe balance composed of Fe and unavoidable impurities, which is for theuse to a holding material of a superconductive electromagnet or asuperconductor, or the like.

Patent document 3 (JP-A-59-205452) discloses a high-strength member foran instrument loaded on an undersea research ship, which contains C:0.15% or less, Si: 0.1 to 2.0%, Mn: 7.0 to 18.0%, Ni: 0.50 to 6.0%, Cr:15.0 to 26.0%, Mo: 0.5 to 4.0%, N: 0.2 to 0.6% and the balancesubstantially composed of Fe, and is subjected to hot working at arolling reduction of 50% or more, wherein the finishing temperature ofthe hot working is from 800 to 1,000° C.

Patent document 4 (JP-A-61-143563) discloses a rust-resistant, ultra-lowtemperature high manganese high-strength steel containing C: 0.20% orless, Si: 0.05 to 2.5%, Mn: 16 to 35%, Cr: 10 to 20%, Ni: 0.1 to 8.0%,N: 0.10 to 0.50%, Al: 0.001 to 0.20%, S: 0.003% or less and the balancecomposed of Fe and unavoidable impurities, which is for the use to aholding material of a superconductive electromagnet or a superconductor,or the like.

Patent document 5 (JP-A-61-170545) discloses an ultra-low temperaturehigh manganese steel excellent in rust resistance, which contains C:0.20% or less, Si: 0.05 to 2.5%, Mn: 9 to 35%, Cr: 10 to 20%, Ni: 0.1 to8.0%, N: 0.001 to 0.50%, Al: 0.001 to 0.20%, Ca: 0.001 to 0.020% and thebalance composed of Fe and unavoidable impurities, for the use to astructure used in a fusion experimental reactor using a superconductiveelectromagnet, or the like.

Patent document 6 (JP-A-61-238943) discloses a high-strengthnon-magnetic stainless steel excellent in rust resistance, whichcontains C: 0.01 to 0.15 wt %, Si: 0.05 to 0.60 wt %, Mn: 16 to 25 wt %,S: 0.010 wt % or less, Ni: 4.0 wt % or less, Cr: 14 to 20 wt %, N: 0.3to 0.6 wt %, O: 0.01 wt % or less, Al: 0.001 to 0.20 wt % and thebalance composed of Fe and unavoidable impurities, and containsnon-metallic inclusions in an area ratio of 0.10% or less, which is forthe use to a precision equipment part (a micromotor shaft, a magnetictape guide, a shaft or the like) that is required to avoid magnetism.

Patent document 7 (JP-A-2004-052097) discloses an interdental brush wirecontaining, by mass, C: 0.07% or less, Si: 0.6% or less, Mn: 13 to 17%,Ni: 2.0 to 5.0%, Cr: 16.0 to 20.0%, Mo: 0.4 to 2.0%, N: 0.3 to 0.60% andCu: 0.3 to 1.0%, which is for the use to the interdental brush wire.

Patent document 8 (JP-A-2004-156086) discloses a non-magnetic stainlesssteel containing C: 0.06% or less, Si: 0.40% or less, Mn: 15.5 to 17%,P: 0.040% or less, S: 0.010% or less, Cu: 0.35 to 2.00%, Ni: 2.50 to4.00%, Cr: 17.0 to 21.0%, Mo+W: 0.5 to 1.5%, N: 0.42 to 0.65%, O: 0.01%or less, sol-Al: 0.05% or less, B: 0.001 to 0.010% and the balancesubstantially composed of Fe, which is for the use to a drill collar foroil well excavation.

As described above, a lot of stainless steels excellent incharacteristics such as corrosion resistance and non-magnetism have beenproposed.

However, the recent oil well excavation region is versatile, and furtherhigh-corrosion resistant and high-strength stainless steels based on theassumption of non-magnetism have been demanded by the industrial world.Furthermore, thevarious types of steels described in the above-mentionedpatent documents 1 to 8 have many problems to be solved. For example,the high-strength austenitic stainless steel of patent document 1 andthe high-strength member for an instrument loaded on an undersearesearch ship of patent document 3 have a concern that workability andcorrosion resistance are deteriorated by crystallization of coarsecarbides due to their excessive C content.

The ultra-low temperature high-strength steel of patent document 2 andthe rust-resistant, ultra-low temperature high manganese high-strengthsteel of patent document 4 have a concern that the requiredcharacteristics of non-magnetism, high strength and corrosion resistanceare not satisfied due to their small N content. The ultra-lowtemperature high-strength steel of patent document 2 has a furtherconcern that corrosion resistance is deteriorated due to its excessiveMn content.

The ultra-low temperature high manganese steel of patent document 5 hasa concern that the required characteristics of non-magnetism, highstrength and corrosion resistance are not satisfied, because the Crcontent is rather small with respect to the Mn content, and the Ncontent is also rather small.

In the high-strength non-magnetic stainless steel of patent document 6,the Ni and N contents are rather small. Further, in the interdentalbrush wire of patent document 7, Mn and Ni contents are excessivelysmall. Moreover, in the non-magnetic stainless steel of patent document8, the Ni and Mo contents are excessively small. Therefore, these alloyshave a concern that the required characteristics of non-magnetism, highstrength and corrosion resistance are not satisfied.

As described above, even according to patent documents 1 to 8, nostainless steel satisfying the required characteristics has beenobtained.

SUMMARY OF THE INVENTION

The invention has been made in view of the above circumstances, and anobject of the invention is to provide a high corrosion-resistant,high-strength and non-magnetic stainless steel having high corrosionresistance, high strength and non-magnetism; a high corrosion-resistant,high-strength and non-magnetic stainless steel product and a method forproducing the same.

In particular, an object of the invention is to provide a highcorrosion-resistant, high-strength and non-magnetic stainless steelwhich blocks the influence of earth magnetism at the time of oil wellevacuation, and not only can be applied to oil well excavation productscovering a wide range of regions, but also is suitable as raw materialsfor various parts (various spring products, VTR guide pins and motorshafts); a high corrosion-resistant, high-strength and non-magneticstainless steel product and a method for producing the same.

In order to solve the above-mentioned problems, the present inventorshave made intensive studies, centering on application of Cr and Mo ascorrosion resistance-improving elements, for realizing high corrosionresistance. However, the inventors have encountered a problem that“non-magnetism which is capable of blocking the influence of earthmagnetism” required for a drill collar and the like of oil wellevacuation and the like cannot be achieved, because an increase in Crcontent and Mo content causes magnetization. Then, the inventors havemade further intensive studies. As a result, it has been found that whena composition balance is adjusted by making use of N and Ni, a stablenon-magnetic austenite single-phase structure is obtained, even in thecase where Cr and Mo are used to obtain high corrosion resistance.

The invention has been made based on such a finding.

Namely the present invention provides a high corrosion-resistant,high-strength and non-magnetic stainless steel containing: C: 0.01% to0.05% by mass, Si: 0.05% to 0.50% by mass, Mn: more than 16.0% by massbut 19.0% by mass or less, P: 0.040% by mass or less, S: 0.010% by massor less, Cu: 0.50% to 0.80% by mass, Ni: 3.5% to 5.0% by mass, Cr: 17.0%to 21.0% by mass, Mo: 1.80% to 3.50% by mass, B: 0.0010% to 0.0050% bymass, O: 0.010% by mass or less, and N: 0.45% to 0.65% by mass, with thebalance substantially composed of Fe and unavoidable impurities, thesteel satisfying the following equations (1) to (4):

[Cr]+3.3×[Mo]+16×[N]≧30   (1)

[Cr]/[C]≧330   (2)

[Cr]/[Mn]>1.0   (3)

([Ni]+3×[Cu])/([Cr]+[Mo])>0.25   (4)

wherein [Cr], [Mo], [N], [C], [Mn], [Ni] and [Cu] represent the contentof Cr, the content of Mo, the content of N, the content of C, thecontent of Mn, the content of Ni, and the content of Cu in the steel interms of mass %, respectively.

The high corrosion-resistant, high-strength and non-magnetic stainlesssteel according to the present invention may further contains at leastone element selected from the group consisting of Ca, Mg and REM in atotal content of 0.0001% to 0.0100% by mass.

The high corrosion-resistant, high-strength and non-magnetic stainlesssteel according to the present invention may further contains at leastone element selected from the group consisting of Nb, V, Ta and Hf in atotal content of 0.1% to 2.0% by mass.

The high corrosion-resistant, high-strength and non-magnetic stainlesssteel according to the present invention may further contains Al in acontent of 0.001% to 0.10% by mass.

The high corrosion-resistant, high-strength and non-magnetic stainlesssteel according to the present invention may further contains at leastone member selected from the group consisting of W and Co in a totalcontent of 0.1% to 3.0% by mass.

The present invention further provides a method for producing a highcorrosion-resistant, high-strength and non-magnetic stainless steelproduct, which includes subjecting the steel according to the presentinvention to working under a temperature condition of 300° C. to 900° C.at a reduction of area of 15% to 40%.

The present invention furthermore provides a high corrosion-resistant,high-strength and non-magnetic stainless steel product obtained bysubjecting the steel according to the present invention to working undera temperature condition of 300° C. to 900° C. at a reduction of area of15% to 40%. Examples of the resulting steel product include oil wellevacuation products, spring products, VTR guide pins, motor shafts andthe like.

The high corrosion-resistant, high-strength and non-magnetic stainlesssteel and the high corrosion-resistant, high-strength and non-magneticstainless steel product according to the invention have theabove-mentioned component composition and satisfies the above-mentionedequations (1) to (4), so that they have high corrosion resistance, highstrength and non-magnetism. Accordingly, they has effects of being ableto block the influence of earth magnetism at the time of oil wellevacuation to be applied to oil well excavation products covering a widerange of regions, and moreover, being suitable as raw materials forvarious parts (various spring products, VTR guide pins and motorshafts).

In accordance with the method for producing a high corrosion-resistant,high-strength and non-magnetic stainless steel product according to theinvention, the resulting steel product can exhibit the same effects asdescribed above.

BEST MODE FOR CARRYING OUT THE INVENTION

A high corrosion-resistant, high-strength and non-magnetic stainlesssteel according to one embodiment of the invention will be describedbelow.

The high corrosion-resistant, high-strength and non-magnetic stainlesssteel according to this embodiment contains the following essentialelements and selective elements and the balance substantially composedof Fe and unavoidable impurities, and satisfies relationship defined byequations (1) to (4) described later. Herein, in the presentspecification, all the percentages defined by mass are the same as thosedefined by weight, respectively.

(Component Composition of High-Corrosion Resistant, High-Strength andNon-Magnetic Stainless Steel, and Reason for Restriction Thereof)

The high corrosion-resistant, high-strength and non-magnetic stainlesssteel according to this embodiment contains C, Si, Mn, Cu, Ni, Cr, Mo, Band N as essential elements, and the balance is substantially composedof Fe and unavoidable impurities. The unavoidable impurities asmentioned herein include, for example, P, S and O.

(1) 0.01%≦C≦0.05% by Mass

C is an essential element which is indispensable as an austenite-formingelement, and contributes to strength. Accordingly, 0.01% by mass isspecified as the lower limit of the content of C. Further, excessiveaddition of C causes coarse carbides to crystallize, therebydeteriorating workability and corrosion resistance. Accordingly, 0.05%by mass is specified as the upper limit of the content of C. The contentof C is more preferably from 0.03% to 0.05% by mass.

(2) 0.05%≦Si≦0.50% by Mass

Si is an essential element added as a deoxidizer for the steel, so that0.05% by mass is specified as the lower limit of the content of Si.However, an excessive content of Si causes a decrease in toughness todeteriorate hot workability, so that 0.50% by mass is specified as theupper limit of the content of Si. The content of Si is more preferablyfrom 0.10% to 0.30% by mass.

(3) 16.0%≦Mn≦19.0% by Mass

Mn is an essential element acting as a deoxidizer for the steel. Inorder to secure the dissolved amount of N, Mn should be contained in anamount of more than 16.0% by mass. On the other hand, Mn deterioratescorrosion resistance, so that 19.0% by mass is specified as the upperlimit of the content of Mn. The content of Mn is more preferably morethan 16.0% by mass but 17.0% by mass or less.

(4) P≦0.040% by Mass

P is an unavoidable impurity, segregates in a grain boundary to heightenthe 2 0 corrosion susceptibility of the grain boundary and deterioratethe toughness.

Accordingly, the content of P is preferably as low as possible. However,an excessive reduction thereof causes an increase in cost, so that thecontent of P is specified as 0.040% by mass or less. The content of P ismore preferably 0.030% by mass or less.

(5) S≦0.010% by Mass

S is an unavoidable impurity, and deteriorates hot workability, so that0.010% by mass is specified as the upper limit of the content of S. Fromthe viewpoint of a balance with production cost, the content of S ismore preferably 0.005% by mass or less.

(6) 0.50%≦Cu≦0.80% by Mass

Cu is an essential element, effective for improving corrosionresistance, particularly corrosion resistance in a reducing acidenvironment, and effective for obtaining an austenite single-phasestructure. Accordingly, 0.50% by mass is specified as the lower limit ofthe content of Cu. On the other hand, excessive addition of Cudeteriorates hot workability, so that 0.80% by mass is specified as theupper limit of the content of Cu.

(7) 3.5%≦Ni≦5.0% by Mass

Ni is an essential element, effective for improving corrosionresistance, particularly corrosion resistance in a reducing acidenvironment, and provides an austenite single-phase structure at thetime of solution treatment. Accordingly, 3.5% by mass is specified asthe lower limit of the content of Ni. On the other hand, excessiveaddition of Ni causes an increase in cost, so that 5.0% by mass isspecified as the upper limit of the content of Ni. The content of Ni ismore preferably from 3.5% to 4.5% by mass, from the viewpoint of abalance between characteristics and cost.

(8) 17.0%≦Cr≦21.0% by Mass

Cr is an essential element from the viewpoint of securing corrosionresistance, and in order to secure the dissolved amount of N, 17.0% bymass is specified as the lower limit of the content of Cr. On the otherhand, excessive addition of Cr impairs hot workability and causes adecrease in toughness, so that 21.0% by mass is specified as the upperlimit of the content of Cr. The content of Cr is more preferably from18.0% to 19.5% by mass.

(9) 1.80%≦Mo≦3.50% by Mass

Mo is an essential element, which provides necessary corrosionresistance and is capable of further improving strength. Accordingly,1.80% by mass is specified as the lower limit of the content of Mo. Onthe other hand, excessive addition of Mo impairs hot workability, andcauses an increase in cost. Accordingly, 3.50% by mass is specified asthe upper limit of the content of Mo. The content of Mo is morepreferably from 2.00% to 2.50% by mass.

(10) 0.0010%≦B≦0.0050% by Mass

B is an essential element effective for improving hot workability of thesteel, so that 0.0010% by mass is specified as the lower limit of thecontent of B. On the other hand, excessive addition of B forms nitridessuch as BN to deteriorate workability, so that 0.0050% by mass isspecified as the upper limit of the content of B. The content of B ismore preferably 0.0030% by mass or less.

(11) O≦0.010% by Mass

O is an unavoidable impurity, which forms harmful oxides which exert anadverse effect on cold workability, fatigue characteristics or the like.Accordingly, the O content should be restrained as low as possible, and0.010% by mass is specified as the upper limit of the content of O. Fromthe viewpoint of a balance with production cost, the content of O ismore preferably 0.007% by mass or less, and still more preferably 0.005%by mass or less.

(12) 0.45%≦N≦0.65% by Mass

N is an essential element necessary for obtaining non-magnetism, highstrength and good corrosion resistance, and 0.45% by mass is specifiedas the lower limit of the content of N. On the other hand, excessiveaddition of N causes N blow, so that 0.65% by mass is specified as theupper limit of the content of N. The content of N is more preferablyfrom 0.50% to 0.60% by mass.

The high corrosion-resistant, high-strength and non-magnetic stainlesssteel according to this embodiment may further contain the followingselective elements, that is to say, at least one element selected fromthe group consisting of Ca, Mg and REM; the group consisting of Nb, V,Ta and Hf; Al; and the group consisting of W and Co.

(13) At Least One Element Selected from the Group Consisting of Ca, Mgand REM in a Total Content of 0.0001% to 0.0100% by Mass

Ca, Mg and REM are selective elements, and elements effective forimproving hot workability of the steel. Accordingly, they may be addedin a total content of 0.0001% by mass or less. However, excessiveaddition of these elements results in saturation of the effect, andconversely decreases hot workability. Accordingly, 0.0100% by mass isspecified as the upper limit of the total content thereof. The totalcontent thereof is more preferably 0.0050% by mass or less.Incidentally, in this embodiment, REM means one containing Ce, La or analloy thereof.

(14) At Least One Element Selected from the Group Consisting of Nb, V,Ta and Hf in a Total Content of 0.1% to 2.0% by Mass

Nb, V, Ta and Hf are selective elements, and these have an effect offorming carbides or carbonitrides to miniaturize grains of the steel,thereby increasing toughness. Accordingly, 0.1% by mass is specified asthe lower limit of the total content of Nb, V, Ta and Hf. On the otherhand, excessive addition of Nb, V, Ta and Hf causes an increase in cost,so that 2.0% by mass in total is specified as the upper limit. Thecontent of Nb, V, Ta and Hf is more preferably 1.0% by mass or less.

(15) 0.001%≦Al≦0.10% by Mass

Al is a strong deoxidizing element, and is also a selective elementwhich is added for decreasing O as much as possible, as needed. For thecontent of Al, 0.001% by mass is specified as the lower limit, at whichthe effect thereof can be confirmed. On the other hand, excessiveaddition of Al deteriorates hot workability, so that 0.10% by mass isspecified as the upper limit of the content of Al. The content of Al ismore preferably 0.050% by mass, and still more preferably 0.010% bymass.

(16) At Least One Element Selected from the Group Consisting of W and Coin a Total Content of 0.1% to 3.0% by Mass

W is a selective element, and has an effect of improving corrosionresistance and forming a carbide or a carbonitride to miniaturizegrains, thereby increasing toughness. Accordingly, W may be added in anamount of 0.1% to 3.0% by mass. On the other hand, excessive addition ofW causes an increase in cost, so that the content of W is morepreferably 2.0% by mass or less.

Co is a selective element, and effective for obtaining an austenitesingle-phase structure to achieve high strength by solid solutionstrengthening. Accordingly, Co may be added as needed. However,excessive addition of Co causes a substantial increase in cost, so that3.0% by mass is specified as the upper limit of the content of Co. Thecontent of Co is more preferably 1.5% by mass or less.

(Component Relationship of High-Corrosion Resistant, High-Strength andNon-Magnetic Stainless Steel, and Reason for Restriction Thereof)

The high corrosion-resistant, high-strength and non-magnetic stainlesssteel according to this embodiment satisfies the following equations (1)to (4):

(17) PI=[Cr]+3.3×[Mo]+16×[N]≧30   equation (1)

PI (Pitting Index) is a value indicating corrosion resistance, anddefined by [Cr], [Mo] and [N]. The larger value shows the bettercorrosion resistance, so that PI is specified as 30 or more. In order tomake it possible to use the steel under a severe corrosive environment,the value of equation (1) is more preferably 33 or more.

(18) [Cr]/[C]≧330   equation (2)

C combines with Cr to form a carbide, thereby decreasing the content ofCr in the matrix and thus causing deterioration of corrosion resistance.For this reason, 2 0 equation (2) becomes a relational expression whichcan be used as an index of corrosion resistance. Accordingly, the largerthe Cr content to the C content is, the more the deterioration ofcorrosion resistance can be inhibited. The value of equation (2) istherefore specified as 330 or more.

(19) [Cr]/[Mn]>1.0   equation (3)

Both Cr and Mn are added in order to sufficiently dissolve N. However,Mn deteriorates corrosion resistance, so that it becomes necessary tobalance with Cr as an element for improving corrosion resistance.Accordingly, in order to sufficiently maintain corrosion resistance bycompensating for deterioration of corrosion resistance caused byaddition of Mn, the value of equation (3) is specified as exceeding 1.0.

(20) ([Ni]+3×[Cu])/([Cr]+[Mo])>0.25   equation (4)

Both Cr and Mo are added for sufficiently securing corrosion resistance.However, associated therewith, stability of an austenite single phasedeteriorates. Accordingly, in order to stabilize the austenite phase, Niand Cu as austenite-forming elements are allowed to be contained inpredetermined amounts, thereby inhibiting deterioration of the stabilityof the austenite single phase. Further, an increase in weight of Cr andaddition of Mo act toward a direction impairing non-magnetism, so thatnon-magnetism is maintained by Ni and Cu. In view of thesecircumstances, equation (4) defines a quantitative relation in which Niand Cu should satisfy with respect to Cr and Mo. The value of equation(4) is specified as exceeding 0.25, but it is more preferably 0.30 ormore.

In this regard, with regard to each element contained in the steel ofthe invention, according to an embodiment, the minimal amount thereofpresent in the steel is the smallest non-zero amount used in theinventive steels as summarized in Tables 1 and 2. According to a furtherembodiment, the maximum amount thereof present in the steel is themaximum amount used in the inventive steels as summarized in Tables 1and 2.

(Method for Producing High-Corrosion Resistant, High-Strength andNon-Magnetic Stainless Steel and High-Corrosion Resistant, High-Strengthand Non-Magnetic Stainless Steel Product Using the Same)

The high-corrosion resistant, high strength and non-magnetic stainlesssteel according to this embodiment is obtained by

(1) melting a steel ingot containing the above-mentioned specifiedcomponents in specified amounts so as to satisfy the specifiedrelations,

(2) processing it to an appropriate shape and size by hot working, andthen,

(3) subjecting it to solution treatment (1050° C. to 1150° C.).

The high-corrosion resistant, high strength and non-magnetic stainlesssteel product according to this embodiment is obtained by, in additionto the above-mentioned steps,

(4) further subjecting the above-mentioned stainless steel to warmworking (300° C. to 900° C., reduction of area: 15% to 40%). Cutting orthe like may be further performed as needed. The reason for specifyingthe lower limit temperature as 300° C. is that the lower workingtemperature contributes to higher strength, whereas deteriorateselongation and drawing, resulting in difficulty in working.

Examples (Preparation of Invention Steels and Comparative Steels)

A 50 kg steel ingot having each component composition (the balance iscomposed of Fe and unavoidable impurities) shown in Tables 1 and 2 wasmelted in a high-frequency induction furnace, and a rod stock having adiameter of 20 mm was prepared by hot forging processing, followed bysolution treatment at 1050° C. to 1150° C. The values of theabove-mentioned equations (1) to (4) are shown together in Table 2. Inthe tables 1 and 2, “-” means that a corresponding element is not addedor unavoidably contained even though it should not be added.

TABLE 1 Component Composition (unit: % by mass) and Values of Equations(1) to (4) C Si Mn P S Cu Ni Cr Mo B O N Inventive 1 0.03 0.18 16.90.002 0.001 0.52 5.0 19.3 1.89 0.0038 0.005 0.48 steel 2 0.02 0.48 16.10.018 0.002 0.65 3.6 18.8 1.94 0.0014 0.008 0.52 3 0.04 0.13 18.7 0.0280.002 0.53 4.5 18.9 2.11 0.0023 0.006 0.54 4 0.03 0.31 18.9 0.037 0.0030.55 4.4 19.3 1.96 0.0021 0.004 0.55 5 0.04 0.21 16.1 0.011 0.003 0.623.6 18.7 2.05 0.0025 0.007 0.55 6 0.02 0.49 16.2 0.009 0.004 0.59 4.920.1 2.77 0.0013 0.003 0.63 7 0.03 0.25 16.3 0.025 0.002 0.61 3.5 18.81.95 0.0021 0.004 0.56 8 0.01 0.12 17.4 0.029 0.008 0.74 5.4 19.8 1.820.0028 0.007 0.64 9 0.05 0.46 18.8 0.032 0.005 0.60 4.6 18.9 2.00 0.00320.008 0.54 10 0.03 0.28 16.0 0.027 0.003 0.58 3.6 18.5 2.16 0.0048 0.0070.55 11 0.05 0.29 17.4 0.023 0.003 0.79 3.8 17.6 2.54 0.0019 0.007 0.4912 0.02 0.28 18.3 0.006 0.004 0.58 4.5 17.9 2.33 0.0024 0.005 0.65 130.04 0.29 18.6 0.027 0.002 0.64 4.9 19.2 2.76 0.0022 0.005 0.55 14 0.030.39 18.9 0.029 0.001 0.61 4.5 19.1 1.94 0.0020 0.004 0.54 15 0.04 0.2218.8 0.020 0.004 0.57 5.0 18.8 2.01 0.0019 0.003 0.57 16 0.05 0.38 17.70.017 0.001 0.55 4.6 18.0 1.85 0.0034 0.001 0.63 17 0.05 0.24 18.5 0.0320.002 0.52 5.0 19.0 2.84 0.0028 0.004 0.53 18 0.03 0.29 18.8 0.030 0.0010.63 4.6 19.2 2.11 0.0031 0.002 0.55 19 0.04 0.27 18.5 0.028 0.003 0.504.4 18.6 2.22 0.0030 0.003 0.54 20 0.02 0.11 16.6 0.025 0.002 0.68 4.119.6 2.03 0.0029 0.003 0.51 Ca, Mg, Nb, V, Ta, (Ni + 3Cu)/ REM Hf Al W,Co PI Cr/C Cr/Mn (Cr + Mo) Inventive 1 Ca: 0.0009 — — W: 1.8 31.2 6431.14 0.31 steel 2 — Nb: 0.48 0.002 — 33.5 940 1.17 0.27 3 — — — — 34.5473 1.01 0.29 4 — — 0.002 — 34.6 643 1.02 0.28 5 — — — — 34.3 468 1.160.26 6 Ca: 0.0020 — — — 39.3 1005 1.24 0.29 7 — — 0.003 — 34.2 627 1.150.26 8 — V: 0.78 — Co: 1.2 36.0 1980 1.14 0.35 9 Mg: 0.0012 — 0.005 —34.1 378 1.01 0.31 10 — — 0.003 — 34.4 617 1.16 0.26 11 — Nb: 0.35 0.002Co: 0.6 33.8 352 1.01 0.31 12 Mg: 0.0009 Ta: 0.52 0.004 — 36.0 895 1.010.31 13 — — — — 37.1 480 1.03 0.31 14 — — 0.003 — 34.1 637 1.01 0.30 15— — 0.002 — 34.6 470 1.00 0.32 16 — V: 0.32 0.001 — 34.2 360 1.02 0.3117 — — — — 36.9 380 1.03 0.30 18 — — 0.004 W: 0.8 35.4 640 1.02 0.30 19— — 0.001 — 34.6 465 1.01 0.28 20 REM: 0.0014 Hf: 0.28 0.003 W: 2.5 35.7980 1.18 0.28

TABLE 2 Component Composition (unit: % by mass) and Values of Equations(1) to (4) C Si Mn P S Cu Ni Cr Mo B O N Inventive 21 0.04 0.22 18.90.025 0.001 0.62 4.9 19.1 2.94 0.0033 0.006 0.56 steel 22 0.04 0.18 16.70.033 0.001 0.57 4.3 18.2 1.88 0.0041 0.004 0.49 23 0.03 0.28 16.3 0.0290.002 0.71 3.6 19.3 1.91 0.0025 0.005 0.54 24 0.04 0.18 16.3 0.014 0.0020.74 3.5 18.8 1.83 0.0016 0.006 0.55 25 0.01 0.47 16.9 0.027 0.003 0.615.5 19.1 2.32 0.0023 0.005 0.52 26 0.04 0.30 17.7 0.032 0.001 0.58 3.917.8 2.10 0.0026 0.003 0.47 Comparative 1 0.09 0.33 14.8 0.023 0.0030.32 3.0 19.4 0.02 — 0.013 0.54 steel 2 0.05 0.43 1.5 0.019 0.004 0.268.5 18.2 0.23 — 0.009 0.04 3 0.07 0.29 1.2 0.027 0.002 0.23 12.1 18.30.03 — 0.008 0.03 4 0.05 0.33 21.0 0.031 0.003 0.23 4.1 16.8 0.43 —0.007 0.46 5 0.03 0.29 19.8 0.022 0.002 0.54 3.7 17.2 1.22 — 0.009 0.486 0.04 0.32 16.2 0.028 0.004 0.11 3.6 18.4 2.41 — 0.006 0.51 7 0.03 0.4317.2 0.021 0.003 0.32 5.2 19.2 1.45 — 0.004 0.49 8 0.04 0.32 16.3 0.0260.002 0.25 3.9 17.3 0.90 — 0.006 0.55 9 0.05 0.51 18.9 0.034 0.004 0.194.8 18.1 1.11 — 0.005 0.50 10 0.03 0.29 16.8 0.039 0.003 0.34 3.4 16.30.33 — 0.003 0.58 Ca, Mg, Nb, V, (Ni + 3Cu)/ REM Ta, Hf Al W, Co PI Cr/CCr/Mn (Cr + Mo) Inventive 21 — — 0.002 — 37.8 478 1.01 0.31 steel 22 Mg:0.017 — — — 32.2 455 1.09 0.30 23 — — 0.001 — 34.2 643 1.18 0.27 24 — —— — 33.6 470 1.15 0.28 25 — Hf: 0.19 0.002 — 35.1 1910 1.13 0.34 26 REM:0.0019 — — Co: 0.8 32.3 445 1.01 0.28 Comparative 1 — — — — 28.1 2161.31 0.20 steel 2 — — — — 19.6 364 12.13 0.50 3 — — — — 18.9 261 15.250.70 4 — — — — 25.6 336 0.80 0.28 5 — — — — 28.9 573 0.87 0.29 6 — — — —34.5 460 1.14 0.19 7 — — — — 31.8 640 1.12 0.30 8 — — — — 29.1 433 1.060.26 9 — — — — 29.8 362 0.96 0.28 10 — — — — 26.7 543 0.97 0.27

Thereafter, warm working was performed under temperature conditions andreductions of area shown in Tables 3 and 4 to prepare materials undertest (working materials). The materials under test were processed tovarious test specimens.

The tensile strength, the 0.2% yield strength and the elongation (%)were determined by preparing a JIS No. 4 test specimen from each of thematerials under test, and measuring the breaking stress at the time whenthe tensile load is applied to a leading edge of the specimen inaccordance with JIS Z 2241.

The magnetic permeability was determined by performing measurement ofthe magnetic permeability according to the VSM method, taking theexternal magnetic field as 2,000 Oe.

The corrosion resistance was evaluated by the 6% ferric chloride test(JIS G 0578) and the 10% oxalic acid etching test (JIS G 0571).

The test results thereof are shown together in Tables 3 and 4.

TABLE 3 Test results 1 Tensile 0.2% Yield Ferric Chloride 10% StrengthStrength Elongation Magnetic Corrosion Oxalic Acid Working Method (MPa)(MPa) (%) Permeability (g/m² · h) Etching Inventive 1 300° C. warmworking-reduction of area 30% 1151 1053 41 1.004 0.14 step steel 2 300°C. warm working-reduction of area 30% 1250 1148 39 1.003 0.29 step 3300° C. warm working-reduction of area 30% 1294 1179 38 1.002 0.25 step4 300° C. warm working-reduction of area 30% 1321 1217 38 1.004 0.26step 5 300° C. warm working-reduction of area 30% 1304 1201 38 1.0060.29 step 6 300° C. warm working-reduction of area 30% 1512 1386 321.002 0.31 step 7 300° C. warm working-reduction of area 30% 1344 123237 1.007 0.29 step 8 300° C. warm working-reduction of area 30% 15361408 30 1.008 0.28 step 9 300° C. warm working-reduction of area 30%1295 1191 38 1.003 0.25 step 10 300° C. warm working-reduction of area30% 1318 1211 37 1.002 0.29 step 11 300° C. warm working-reduction ofarea 30% 1176 1078 41 1.004 0.25 step 12 300° C. warm working-reductionof area 30% 1560 1430 30 1.006 0.24 step 13 300° C. warmworking-reduction of area 30% 1331 1217 38 1.003 0.26 step 14 300° C.warm working-reduction of area 30% 1298 1190 37 1.004 0.25 step 15 300°C. warm working-reduction of area 30% 1368 1254 36 1.006 0.25 step 16300° C. warm working-reduction of area 30% 1523 1389 31 1.003 0.25 step17 300° C. warm working-reduction of area 30% 1272 1166 38 1.002 0.26step 18 300° C. warm working-reduction of area 30% 1322 1211 37 1.0070.26 step 19 300° C. warm working-reduction of area 30% 1296 1188 381.003 0.25 step 20 300° C. warm working-reduction of area 30% 1224 112240 1.007 0.30 step 21 300° C. warm working-reduction of area 30% 13481236 36 1.007 0.25 step 22 300° C. warm working-reduction of area 30%1176 1078 43 1.002 0.27 step 23 300° C. warm working-reduction of area30% 1299 1182 39 1.002 0.30 step 24 300° C. warm working-reduction ofarea 30% 1320 1210 36 1.005 0.29 step 25 300° C. warm working-reductionof area 30% 1248 1144 38 1.002 0.28 step 26 300° C. warmworking-reduction of area 30% 1128 1034 39 1.002 0.25 step Comparative 1300° C. warm working-reduction of area 30% 1345 1233 35 1.015 1.3 stepsteel 2 300° C. warm working-reduction of area 30% 877 768 51 1.135 15.0step 3 300° C. warm working-reduction of area 30% 943 892 49 1.007 1.5step 4 300° C. warm working-reduction of area 30% 1175 1087 41 1.004 4.3step 5 300° C. warm working-reduction of area 30% 1189 1101 40 1.005 3.9step 6 300° C. warm working-reduction of area 30% 1204 1108 39 1.022 2.1step 7 Working temperature 250° C.- 1401 1345 17 1.018 0.4 stepreduction of area 30% 8 Working temperature 950° C.- 1189 1008 41 1.0271.4 ditch reduction of area 30% 9 Working temperature 300° C.- 1064 97143 1.035 0.5 step reduction of area 10% 10 Working temperature 300° C.-1389 1312 19 1.048 4.1 ditch reduction of area 50%

TABLE 4 Test results 2 Tensile 0.2% Yield Ferric Chloride 10% StrengthStrength Elongation Magnetic Corrosion Oxalic Acid Working Method (MPa)(MPa) (%) Permeability (g/m² · h) Etching Inventive 1 900° C. warmworking-reduction of area 30% 1085 982 43 1.003 0.35 step steel 2 900°C. warm working-reduction of area 30% 1175 1059 41 1.008 0.32 step 3900° C. warm working-reduction of area 30% 1213 1097 38 1.007 0.31 step4 900° C. warm working-reduction of area 30% 1245 1120 39 1.002 0.30step 5 900° C. warm working-reduction of area 30% 1235 1117 39 1.0020.30 step 6 900° C. warm working-reduction of area 30% 1421 1287 361.003 0.26 step 7 900° C. warm working-reduction of area 30% 1263 114439 1.002 0.30 step 8 900° C. warm working-reduction of area 30% 14431307 35 1.002 0.26 step 9 900° C. warm working-reduction of area 30%1222 1109 40 1.007 0.31 step 10 900° C. warm working-reduction of area30% 1242 1121 38 1.002 0.30 step 11 900° C. warm working-reduction ofarea 30% 1105 1001 43 1.004 0.34 step 12 900° C. warm working-reductionof area 30% 1466 1328 35 1.003 0.26 step 13 900° C. warmworking-reduction of area 30% 1247 1128 40 1.004 0.30 step 14 900° C.warm working-reduction of area 30% 1214 1099 40 1.003 0.31 step 15 900°C. warm working-reduction of area 30% 1286 1164 39 1.002 0.29 step 16900° C. warm working-reduction of area 30% 1422 1290 36 1.004 0.26 step17 900° C. warm working-reduction of area 30% 1195 1083 40 1.003 0.31step 18 900° C. warm working-reduction of area 30% 1250 1129 39 1.0040.30 step 19 900° C. warm working-reduction of area 30% 1218 1103 411.002 0.31 step 20 900° C. warm working-reduction of area 30% 1150 104243 1.007 0.33 step 21 900° C. warm working-reduction of area 30% 12601143 38 1.002 0.30 step 22 900° C. warm working-reduction of area 30%1105 1001 43 1.003 0.34 step 23 900° C. warm working-reduction of area30% 1210 1101 40 1.004 0.31 step 24 900° C. warm working-reduction ofarea 30% 1240 1123 39 1.002 0.30 step 25 900° C. warm working-reductionof area 30% 1173 1062 42 1.007 0.32 step 26 900° C. warmworking-reduction of area 30% 1060 970 45 1.002 0.35 step Comparative 1900° C. warm working-reduction of area 30% 1243 1147 38 1.017 2.40 ditchsteel 2 900° C. warm working-reduction of area 30% 775 682 62 1.018 18.9ditch 3 900° C. warm working-reduction of area 30% 841 806 50 1.005 2.3ditch 4 900° C. warm working-reduction of area 30% 1017 962 48 1.003 5.8ditch 5 900° C. warm working-reduction of area 30% 1043 977 46 1.004 4.1step 6 900° C. warm working-reduction of area 30% 1023 982 47 1.014 2.8step 7 8 9 10

(Evaluation)

Inventive Steels 1 to 26 satisfied the required characteristics for allof strength (tensile strength≧1050 MPa, 0.2% yield strength≧968 MPa),workability (elongation≧25), non-magnetism (magnetic permeability≦1.010)and corrosion resistance (ferric chloride corrosion<0.5, 10% oxalic acidetching: step). Inventive Steels 1 to 26 contained the componentsdefined in Tables 1 and 2 in predetermined amounts, and satisfiedequations (1) to (4) defined in Tables 1 and 2. It is thereforeconceivable that corrosion resistance, strength and non-magnetism couldbe achieved at the same time. Accordingly, it has become clear thatInventive Steels 1 to 26 block the influence of earth magnetism at thetime of oil well evacuation, and not only can be applied to oil wellexcavation products covering a wide range of regions, but also aresuitable as raw materials for various parts (various spring products,VTR guide pins and motor shafts).

On the other hand, Comparative Steels 1 to 10 did not satisfy therequired characteristic for any one of strength (tensile strength 1050MPa, 0.2% yield strength 968 MPa), workability (elongation 25),non-magnetism (magnetic permeability≦1.010) and corrosion resistance(ferric chloride corrosion<0.5, 10% oxalic acid etching: step). Thereason for this is considered to be that Comparative Steels 1 to 10 didnot contain the components defined in Table 2 in predetermined amounts,or did not satisfy any one of equations (1) to (4).

For example, Comparative Steel 1 did not satisfy equation 1 because ofits small Mo content, and further did not satisfy equation 2 because ofits excessive C content. Corrosion resistance is therefore considered tobe impaired even when the Mn content is small. Incidentally, althoughComparative Steel 1 did not satisfy equation 4, it satisfied therequired characteristic for magnetic permeability.

Comparative Steel 2 contained Cr essential for securing corrosionresistance in a predetermined amount, but did not satisfy equation 1because of its small Mo and N contents. Corrosion resistance istherefore considered to be impaired. Further, high magnetic permeabilityof Comparative Steel 2 is considered to be caused by the small Ncontent.

Comparative Steel 3 contained Cr essential for securing corrosionresistance in a predetermined amount, but did not satisfy equation 1because of its small Mo and N contents, and did not satisfy equation 2because of its excessive C content. Corrosion resistance is thereforeconsidered to be impaired.

Comparative Steels 4 and 5 did not satisfy equations (1) and (3) becauseof their excessively small Mo content, excessive Mn content and rathersmall Cr content. Corrosion resistance is therefore considered to beimpaired.

Comparative Steel 6 did not satisfy equation (4) because of itsexcessively small Cu content. Corrosion resistance is thereforeconsidered to be impaired.

Comparative Steel 7 satisfied equations (1) to (4), and satisfied therequired characteristics of high corrosion resistance, non-magnetism andhigh strength, although the Cu, Ni and Mo contents were outside thepredetermined ranges. However, it was revealed that Comparative Steel 7was decreased in elongation to cause difficulty in working, which wasunsuitable for actual production, because of its low workingtemperature.

Comparative Steel 8 did not satisfy equation (1), because of itsexcessively small Cu and Mo contents. Corrosion resistance is thereforeconsidered to be impaired. Further, in Comparative Steel 8, the workingtemperature was increased to 950° C. However, it was confirmed that anincrease in working temperature was not so much effective for anincrease in strength.

Comparative Steels 9 and 10 did not satisfied equation (1) because ofits excessively small Mo content, did not satisfy equation (3) inrelation to the balance of the components, and was excessively small inCu content. Corrosion resistance is therefore considered to be impaired.Further, both of these were high in magnetic permeability. Incidentally,in Comparative Steel 9, the reduction of area was as low as 10%,although the working temperature was low. It is therefore conceivablethat deterioration of workability did not occur by high elongation andwork hardening. On the other hand, in Comparative Steel 10, the workingtemperature was low, and moreover, the reduction of area was as high as50%. It was therefore revealed that Comparative Steel 10 was increasedin strength by work hardening, but decreased in elongation to causedifficulty in working, which was unsuitable for actual production.

Although one embodiment of the invention has been described above, theinvention is not construed as being limited to the above-mentionedembodiment, and all modifications are possible based on the usualknowledge of those skilled in the art without departing from the spiritthereof. Such modifications should be construed as being included in thescope of the invention.

The high corrosion-resistant, high-strength and non-magnetic stainlesssteel, the high corrosion-resistant, high-strength and non-magneticstainless steel product and the method for producing the same, accordingto the invention, has the predetermined component composition, and thepredetermined mutual relationship of the components is adjusted.Accordingly, the industrial use value thereof is high for steel productmanufacturers. The high corrosion-resistant, high-strength andnon-magnetic stainless steel according to the invention is expected tobe applied to oil well excavation products and steel products such asspring, shaft, bolt and screw products.

The present application is based on Japanese Application No. 2009-108189filed Apr. 27, 2009, Japanese Application No. 2009-123661 filed May 22,2009 and Japanese Application No. 2010-015591 filed Jan. 27, 2010 thecontents thereof being incorporated herein by reference.

1. A high corrosion-resistant, high-strength and non-magnetic stainlesssteel comprising: C: 0.01% to 0.05% by mass, Si: 0.05% to 0.50% by mass,Mn: more than 16.0% by mass but 19.0% by mass or less, P: 0.040% by massor less, S: 0.010% by mass or less, Cu: 0.50% to 0.80% by mass, Ni: 3.5%to 5.0% by mass, Cr: 17.0% to 21.0% by mass, Mo: 1.80% to 3.50% by mass,B: 0.0010% to 0.0050% by mass, O: 0.010% by mass or less, and N: 0.45%to 0.65% by mass, with the balance substantially composed of Fe andunavoidable impurities, the steel satisfying the following equations (1)to (4):[Cr]+3.3×[Mo]+16×[N]≧30   (1)[Cr]/[C]≧330   (2)[Cr]/[Mn]>1.0   (3)([Ni]+3×[Cu])/([Cr]+[Mo])>0.25   (4) wherein [Cr], [Mo], [N], [C], [Mn],[Ni] and [Cu] represent the content of Cr, the content of Mo, thecontent of N, the content of C, the content of Mn, the content of Ni,and the content of Cu in the steel in terms of mass %, respectively. 2.The high corrosion-resistant, high-strength and non-magnetic stainlesssteel according to claim 1, which further comprises at least one elementselected from the group consisting of Ca, Mg and REM in a total contentof 0.0001% to 0.0100% by mass.
 3. The high corrosion-resistant,high-strength and non-magnetic stainless steel according to claim 1,which further comprises at least one element selected from the groupconsisting of Nb, V, Ta and Hf in a total content of 0.1% to 2.0% bymass.
 4. The high corrosion-resistant, high-strength and non-magneticstainless steel according to claim 2, which further comprises at leastone element selected from the group consisting of Nb, V, Ta and Hf in atotal content of 0.1% to 2.0% by mass.
 5. The high corrosion-resistant,high-strength and non-magnetic stainless steel according to claim 1,which further comprises Al in a content of 0.001% to 0.10% by mass. 6.The high corrosion-resistant, high-strength and non-magnetic stainlesssteel according to claim 2, which further comprises Al in a content of0.001% to 0.10% by mass.
 7. The high corrosion-resistant, high-strengthand non-magnetic stainless steel according to claim 3, which furthercomprises Al in a content of 0.001% to 0.10% by mass.
 8. The highcorrosion-resistant, high-strength and non-magnetic stainless steelaccording to claim 4, which further comprises Al in a content of 0.001%to 0.10% by mass.
 9. The high corrosion-resistant, high-strength andnon-magnetic stainless steel according to claim 1, which furthercomprises at least one member selected from the group consisting of Wand Co in a total content of 0.1% to 3.0% by mass.
 10. The highcorrosion-resistant, high-strength and non-magnetic stainless steelaccording to claim 2, which further comprises at least one memberselected from the group consisting of W and Co in a total content of0.1% to 3.0% by mass.
 11. The high corrosion-resistant, high-strengthand non-magnetic stainless steel according to claim 3, which furthercomprises at least one member selected from the group consisting of Wand Co in a total content of 0.1% to 3.0% by mass.
 12. The highcorrosion-resistant, high-strength and non-magnetic stainless steelaccording to claim 4, which further comprises at least one memberselected from the group consisting of W and Co in a total content of0.1% to 3.0% by mass.
 13. The high corrosion-resistant, high-strengthand non-magnetic stainless steel according to claim 5, which furthercomprises at least one member selected from the group consisting of Wand Co in a total content of 0.1% to 3.0% by mass.
 14. The highcorrosion-resistant, high-strength and non-magnetic stainless steelaccording to claim 6, which further comprises at least one memberselected from the group consisting of W and Co in a total content of0.1% to 3.0% by mass.
 15. The high corrosion-resistant, high-strengthand non-magnetic stainless steel according to claim 7, which furthercomprises at least one member selected from the group consisting of Wand Co in a total content of 0.1% to 3.0% by mass.
 16. The highcorrosion-resistant, high-strength and non-magnetic stainless steelaccording to claim 8, which further comprises at least one memberselected from the group consisting of W and Co in a total content of0.1% to 3.0% by mass.
 17. A method for producing a highcorrosion-resistant, high-strength and non-magnetic stainless steelproduct, which comprises subjecting the steel according to claim 1 toworking under a temperature condition of 300° C. to 900° C. at areduction of area of 15% to 40%.
 18. A high corrosion-resistant,high-strength and non-magnetic stainless steel product obtained bysubjecting the steel according to claim 1 to working under a temperaturecondition of 300° C. to 900° C. at a reduction of area of 15% to 40%.